1. Field of the Application
The present application relates to the rotor blades of an axial turbomachine, more particularly to the stator of an axial turbomachine. The present application also relates to a stator and an axial turbomachine comprising the stator. The present application relates to the angular setting of the blades of an axial turbomachine. The present application also relates to a method of assembling the axial turbomachine, particularly its stator(s).
2. Description of Related Art
In order to achieve high performance, axial turbomachines have several compressors and possibly several turbines which respectively compress and expand air. Each compressor and each turbine commonly has several rows of alternating rotor and stator blades. The pitch angles of the blades on successive stages differ incrementally, thereby gradually compressing the air before it enters the combustion chamber and gradually expanding the exhaust gas.
The pitch is a factor that is calculated for each blade row in order to optimise the efficiency of a given row, and the overall performance of a turbomachine. To construct such a row, several solutions are possible. For example, the array can be fabricated from blades welded to a ferrule, housing or rotor. The blades may also be attached with threaded studs or lockbolts. By providing each blade with two fixing pins it is prevented from rotating. However, this solution is particularly heavy because of the existence of the second fixing pin.
To save weight, it is advantageous to use only one fixing pin. However, this latter can no longer prevent the blade from rotating so that it maintains its pitch. The pitch may nevertheless be maintained by fitting the blade with a platform which is placed in an annular groove the shoulders of which offer an abutment at the corners of the rectangle.
Patent EP 1936121 B1 discloses a turbomachine having such a blade with a platform housed in such an annular groove. The blade is fastened by means of a nut screwed onto its threaded shaft. But this solution has manufacturing constraints. It requires a groove, thereby involving thickening in one place. If one of the materials of which a platform or the groove is made has insufficient hardness, this material may be deformed as the nut is being tightened. Therefore, the accuracy of the blade pitch may be degraded.
Although great strides have been made in the area of blades for axial turbomachines, many shortcomings remain.